Marattialean Tree Ferns Research Articles

The first Palaeodictyoptera (Insecta) from the late Carboniferous of Ogassa (Catalonia, Spain)

A new species of palaeodictyopteridan insect, Heolus martinclosasi sp. nov., based on a partial wing, has been identified in the uppermost Pennsylvanian (Stephanian C local stage) deposits of the Castellar de N’Hug-Camprodon Basin, located in the Surroca-Ogassa coalfield within the Pyrenees of Catalonia, Spain. This species belongs to the Palaeodictyoptera, and is the first of this order described from the Paleozoic deposits of Spain. Heolus martinclosasi sp. nov. is the second species within the relatively small Heolidae family, originally described by Handlirsch in 1906, in the USA. This new species was found alongside remains of in situ fossil plants such as Calamites suckowii, Sphenophyllum oblongifolium, and marattialean tree ferns, all of which grew between river channels. This suggests that these insects possibly lived in lake-like, permanently inundated floodplain deposits.

Physiological selectivity and plant–environment feedbacks during Middle and Late Pennsylvanian plant community transitions

Abstract A series of vegetation changes take place in tropical ecosystems during the Pennsylvanian Subperiod. The most notable change, recognizable from palynology and plant macrofossils at the Middle and Late Pennsylvanian boundary in the Illinois Basin, is the extirpation, or local extinction, of certain lineages of arborescent lycopsids, followed by their replacement by stem group marattialean tree ferns. The leading hypothesis suggests a significant change in precipitation regime as the cause. To test this hypothesis, we examine the vascular anatomy and physiology of key lineages of Pennsylvanian plants: the sphenopsids, tree ferns, cordaitaleans, medullosans, lycophytes and extrabasinal stem group coniferophytes. Using scanning electron and light microscopy of fossilized anatomy, we provide new data on these plants’ vascular systems, quantifying their physiological capacity and drought resistance. We find that three Pennsylvanian plant lineages – the medullosans, arborescent lycopsids and Sphenophyllum – contain high hydraulic conductivity but are vulnerable to drought-induced damage, whereas others are resistant, including stem group tree ferns and coniferophytes. Relative abundance changes among these plants were likely driven by drought, and differences in water use efficiency would have amplified drought events as plant communities changed. The interaction of physiological selectivity and positive feedback between aridity and drought tolerance likely played a significant role in Late Paleozoic floral changes.

Plant taphonomy and palaeoecology of Pennsylvanian wetlands from the Erillcastell Basin of the eastern Pyrenees, Catalonia, Spain

The Pennsylvanian flora from the intramontane Erillcastell Basin in the eastern Pyrenees (Catalonia, Spain) is described in a palaeoenvironmental context based on a combined study of sedimentology, plant taphonomy and paleoecology. This basin differs from other Pyrenean basins of this age in comprising a wide array of fluvial channel and floodplain-related facies, with a limited development of peat mire facies. Both late Moscovian and early Ghzelian successions are rich in diverse calamitalean remains (mainly Calamites cistii and C. suckowii, in addition to C. undulatus in the Moscovian) and pecopterid foliage (mainly Polymorphopteris polymorpha) corresponding to marattialean tree ferns. An unusual feature of the fluvial channel assemblages is the common occurrence of arborescent lycopsids, especially Sigillaria brardii, in association with Calamites species, which presumably occupied riparian niches. Palaeotopographic, drainage and climatic constraints of the Erillcastell Basin may explain this unusual ecological distribution of Sigillaria brardii, which is mostly associated with peat mires and oxbow lakes in other coeval intramontane South European basins. Findings improve knowledge of intermontane forest ecosystems during the Middle to Late Pennsylvanian transition.

Dominance-diversity architecture of a mixed hygromorphic-to-xeromorphic flora from a botanically rich locality in western equatorial Pangea (lower Permian Emily Irish site, Texas, USA

Here we describe the Leonardian-age flora from “Emily Irish” (Russell Ranch), a small oxbow lake deposit, which is believed to be one of the most extensively collected, single-excavation floras of this age from any place in the world, including ca. 5200 hand specimens housed at the US National Museum of Natural History. The flora is dominated by a mixture of xeromorphic and meso-hygromorphic elements. The xeromorphs include conifers, taeniopterids, cordaitaleans, and noeggerathialeans. The mesomorphic-to-hygromorphic elements include marattialean tree ferns, sphenopsids, lycopsids, callipterids, and medullosan pteridosperms. This co-dominance of hygromorphic and xeromorphic elements is made especially conspicuous by the intimate co-mingling of plant remains from each group on the same hand specimens, and by the relative preservation-state of the macrofossils, which does not differ between the two groups. These observations suggest that they inhabited the same landscape immediately surrounding the depositional environment, and were likely only differentiated by microhabitat. We suggest that the Emily Irish flora grew under seasonally dry climate, but that areas adjacent to the lake and feeder streams retained sufficient moisture to support patches of taxa requiring consistently high soil moisture. These patches, thus, were embedded within a landscape of periodic moisture deficit that supported vegetation composed mostly of xeromorphic elements. This is more likely than requiring the xeromorphic taxa to be transported to the site from extrabasinal habitats, the nearest of which were hundreds of kilometers away at the time the deposit formed.

T0 Early Permian coal-forest preserved in situ in volcanic ash bed in the Wuda Coalfield, Inner Mongolia, China

An early Permian tuff bed between Coal 7 and Coal 6 of the Wuda Coalfield in Inner Mongolia bears T0 peat-forming vegetation preserved in situ. Documentation of the fossil record uncovered in an area of about 80 m2 shows 14 morphotaxa representing 11 whole-plant species with a wide variety of growth forms. The uncovered phytocoenosis is interpreted as a forest dominated by cordaites as the tallest trees, the remains of which covered over 50% of the excavated area. Marattialean tree ferns represent the lower canopy that was not taller than about 3 m. This storey fills gaps between cordaites and covers over 20% of the area. A rare element of lower canopy taxa was the cycadophyte genus Pterophyllum represented by a single plant. Poorly developed herbaceous groundcover includes Sphenophyllum oblongifolium, and four small fern species mostly with sphenopteroid type of foliage. Although members of the herbaceous layer covered only 7% of the excavated area, it was the most diverse storey of the peat-forming forest. Considering the small area excavated, along with the higher diversity known from the same tuff bed in the adjacent, former opencast mine, it appears that species richness in the forest was comparable to some of the less diverse Westphalian peat-forming floras in Euramerica.

Modeled physiological mechanisms for observed changes in the late Paleozoic plant fossil record

Earth’s tropical forests repeatedly restructured on 105- to 107-year timescales during the Late Paleozoic Ice Age (340–280 Ma). Although it is established that these ancient plants responded to an evolving climate, their thresholds for physiological functioning and how such thresholds led to vegetation-climate feedbacks warrants further investigation. Here, we evaluate the physiology of seven plant types that dominated Middle Pennsylvanian through early Permian tropical lowland ecosystems. We apply taxa-specific leaf morphologic and geochemical measurements, time-specific atmospheric pCO2, pO2, and O2:CO2, and site-specific meteorology to Paleo-BGC, a modified version of the process-based ecosystem model Biome-BGC 4.2.1. Our study reveals four major findings. (1) The existence of pCO2 and precipitation thresholds for loss of physiological viability that provide a mechanism for replacement of wet-adapted lycopsids and medullosans by marattialean tree ferns, which were tolerant of periodic drought, and the subsequent dominance of seasonally dry-adapted cordaitaleans and conifers. These thresholds are relevant to both vegetation turnovers within glacial-interglacial cycles of the Pennsylvanian and to major restructuring events through the later Carboniferous and early Permian coincident with intensifying paleotropical aridification. (2) Under drier conditions, the combination of higher drought tolerance and primary productivity for marattialean tree ferns, conifers, and cordaitaleans provided an ecophysiological advantage over lycopsids and medullosans. (3) Our results further indicate that, although the shift to more drought-tolerant plants in the Late Pennsylvanian and early Permian could have led to increased biomass and surface runoff, their ability to affect climate was likely limited by aridity and changes in vegetation density. (4) Finally, our modeling shows that atmospheric pCO2 has a larger effect on physiological functioning than pO2. These findings highlight the unique insight into extinct plant function gained by coupling empirical measurements with ecosystem modeling and, in turn, the potential to physiologically constrain paleo-vegetation shifts previously inferred from the paleobotanical record.

An upright psaroniaceous stump and two surrounding pecopteroids from the early Permian Wuda Tuff Flora

An upright Psaronius stump was discovered in the upper part of Taiyuan Formation (Asselian) of Wuda Coalfield, Inner Mongolia, China. The stump is 47 cm high and truncated at the upper part of the ash layer in which it is preserved. At the height of 38 cm, the stem possesses a stelar configuration comprised of 3~4 cycles in 5 orthostichies. The Wuda Psaronius stump rapidly widens at the base until it attains a stable axial diameter; a root mantle is present in the proximal zone of primary body expansion, but not distal to that zone. This architecture is further demonstrated by a prostrate Psaronius trunk almost 7 m long with a stable stem diameter and two rows of frond scars visible over most of its length. This developmental mode is seen among extant leptosporangiate tree ferns but differs from that previously documented among North American Pennsylvanian marattialean tree ferns whereby the primary body of Psaronius stems increases continually in width towards the apex and is buttressed by a thick root mantle that compensates for the obconical nature of the stem. Two types of pecopteroid fronds associated with the Psaronius stump are identified as Pecopteris cf. polymorpha and Pecopteris orientalis based on their pinnule morphology. The Pecopteris orientalis frond possesses a penultimate rachis with stewartiopteroid anatomy and is more likely to be the leaf of the Psaronius stump based on a recently reported Psaronius specimen with stem and frond in connection from the same locality.

A Middle Pennsylvanian (early Asturian) tropical dry forest, Atokan-Desmoinesian boundary, Illinois Basin, USA

Six late Atokan (early Asturian) floras from seasonally dry environments are described and quantitatively analysed from adpressions and palynomorphs. Collections are from the eastern margin of the Illinois Basin, USA, in an 80 km N-S transect. Plant fossils occur in sedimentary rocks below the underclay (paleosol) of the Minshall-Buffaloville Coal Member (thus, not “roof-shale” assemblages), uppermost Brazil Formation. Growth of floras under season dryness is indicated by outcrop and lithological features that suggest deposition in flashy discharge streams, including intraformational conglomerates, plant fossils that cross bedding planes indicating rapid, episodic burial, and local rhythmically laminated sediments. Common charcoal clasts are consistent with seasonal climate. Cordaitalean foliage dominates the macroflora, accompanied by the dryland elements Lesleya sp., Taeniopteris sp. cf. T. multinervia, and Sphenopteridium sp. Two unusual forms of foliage are presumed to be rare or novel dryland species. Small numbers of wetland/periwetland taxa include calamitaleans, Linopteris neuropteroides, Karinopteris/Eusphenopteris sp., marattialean fern foliage, Senftenbergia plumosa, cf. Zeilleria avoldensis and Sphenopteris sp. The palynoflora is dominated by marattialean tree ferns, wetland plants with broad dispersal capacities and environmental tolerances. Subdominant elements also have strong wetland affinities. Palynoflora-macroflora mismatches may reflect primary ecology, palynomorph reworking, or both. The occurrence of these floras near the Atokan-Desmoinesian (~ Bolsovian-Asturian) boundary coincides with an array of physical and geochemical data that indicate change from weak rainfall seasonality to marked seasonality at all phases of glacial-interglacial cycles, reflected prominently in the stratigraphic record from the localities studied.

Paleoecological and paleoenvironmental interpretation of three successive macrofloras and palynofloras from the Kola Switch locality, lower Permian (Archer City Formation, Bowie Group) of Clay County, Texas, USA

Fossil floras have been recovered from a unique deposit of early Permian age in North-Central Texas. The site, Kola Switch, preserves three distinct floras in different lithofacies, in a succession from a single outcrop. The sedimentary environment appears to be a floodplain channel fill of primarily siltstones and claystones. The lowermost flora, preserved in a kaolinitic siltstone, indicates active water flow. It is dominated by plants typical of well-drained substrates, dominated by Sphenopteris germanica, and contains no wetland elements. The middle flora is from a finely laminated carbonaceous claystone and is dominated by marattialean tree ferns, with no elements from habitats typical of seasonal moisture availability. It contains no roots and appears to have formed as a floating peat mat. The upper flora is a mixed assemblage of wetland taxa and those typical of well-drained soil environments or a seasonal rainfall regime. Unlike the two lower floras, it has a relatively even distribution of dominance and is the most diverse of the three assemblages. Palynofloras also were recovered from each of these beds. The palynofloras, although varying between and even within the beds, indicate a common background species pool during the time interval sampled, suggesting that these distinct floras reflect local changes in microhabitat conditions under a constant climatic background. The palynoflora from each bed has characteristics in common with the macroflora of that bed, but also distinct differences. Together, the macroflora and microflora provide an unusually broad picture of this site through time. Kola Switch compares favorably with the recently described flora from the nearby Sanzenbacher Ranch site of approximately the same age and also with floras of Rotliegend age from Central Europe.

Vegetational zonation in a swamp forest, Middle Pennsylvanian, Illinois Basin, U.S.A., indicates niche differentiation in a wetland plant community

A rich fossil flora occurs in the roof shale of the Middle Pennsylvanian (Moscovian) age, Springfield Coal flanking the Galatia channel, a river deposit approximately 1km in width and 150km long, partially contemporaneous with the Springfield peat swamp. Siltstone and sandstone, >30m thick, were deposited in the channel during the final estuarine phase. The river formed under seasonal subhumid climate during early deglaciation as marine waters retreated from the land surface. It existed continuously through glacial maximum, under increasingly humid climate, as a low-sediment or black-water river with peat along its flanks. During early deglaciation, under subhumid climate and sea-level rise, the river became a sediment-laden estuary, drowning the peat swamp and burying vegetation in place under extensive mudflats. This buried flora was studied in three underground mines in southern Illinois, permitting vegetation to be characterized spatially. Three transects, comprising 100 sites, a total linear distance of ~12km, reveal distinct zonation perpendicular to the channel margin. An innermost belt, 0.5 to 2.5km wide, consists almost exclusively of the pteridosperm Neuropteris flexuosa. North of a river bend, three belts succeed the N. flexuosa zone: mixed pteridosperms and marattialean tree ferns; mixed arborescent lycopsids and marattialians; lycopsids with rare marattialians. South and inside the same bend, N. flexuosa is succeeded by mixed lycopsids, particularly Sigillaria, and marattialean ferns. Within the transects, marattialian ferns have wider distribution than other groups, suggesting broader environmental tolerances. Neuropteris flexuosa channel-margin mono-dominance may reflect high sedimentation rates, elevated nutrient conditions, or floating-seed dispersal. Lycopsid dominance in interior areas conforms with tolerance of deep, standing water. The spatial scale examined affects our perception of community assembly. Overall, distinct vegetational zonation suggests niche-assembly; however, within vegetational bands, there is considerable small-scale spatial variation suggesting stochastic properties.

Plant Fossils from the Pennsylvanian–Permian Transition in Western Pangea, Abo Pass, New Mexico

Plant fossils are described from five stratigraphic levels spanning the Pennsylvanian–Permian boundary in Abo Canyon, New Mexico. Charles B. Read collected the fossils in 1940 and 1941; Read’s field notes cannot be located. A combination of Read’s bed numbering pattern, his notes in the collections, and collection taxonomic composition permits them to be placed in an oldest to youngest sequence. The youngest fossils, from the Abo Formation of early Permian age, anchor the collection stratigraphically. A collection labeled “Base of Red Magdalena” is most likely equivalent to the modern Bursum Formation, thus immediately below the Abo. The three remaining collections are from the Upper Pennsylvanian portion of the Atrasado Formation. All collections are dominated or codominated by plants typical of environments with seasonal moisture stress and record increasing moisture limitation through time. Conifers, Sphenopteris germanica, and mixoneurid odontopterids are common to abundant in pre-Abo Formation collections. These same collections also contain wet-substrate taxa, particularly calamitaleans and marattialean tree ferns, with arborescent lycopsids in the oldest collection. The middle three collections contain the remains of microconchids / spirorbids, snails, ostracods, and conchostracans closely associated with the plant remains, indicating brackish to marine salinities at the burial sites of the organics. The Abo Pass collections document Pennsylvanian–Permian floristic changes in the western Pangean equatorial belt, an important point of comparison to better studied floras from this same interval in central Pangea (eastern United States and Europe). Most of the plants in the western equatorial assemblages are the same as those of similar age from west central to central Pangea (Euramerica), indicating a widespread tropical biogeographic province at this time, but within which there were several distinct biomes.

HERBIVOROUS AND DETRITIVOROUS ARTHROPOD TRACE FOSSILS ASSOCIATED WITH SUBHUMID VEGETATION IN THE MIDDLE PENNSYLVANIAN OF SOUTHERN BRITAIN

ABSTRACT We describe plant–arthropod associations from the Middle Pennsylvanian (late Bolsovian–early Asturian) Pennant Sandstone Formation of southern Britain. Our material comprises calcified cordaitaleans and tree-fern axes, preserved in braided channel deposits, and interpreted as remains of subhumid riparian vegetation distinct from that of coeval coal swamps. The first plant–arthropod association, attributed to herbivorous insects, comprises cambial damage to cordaitalean leafy branches, resulting in traumatic wound response. The second and most widespread association, attributable to detritivorous oribatid mites, includes tunnels and galleries containing widely scattered, clustered, or densely packed microcoprolites within the inner root mantle of marattialean tree ferns and cordaitalean trunks and branches. Diameter data for tunnels and microcoprolites are multimodal, recording four or five instars of oribatid mites that parallel instar-based fecal pellet and body lengths in modern taxa. The third...

A conifer-dominated palynological assemblage from Pennsylvanian (late Moscovian) alluvial drylands in Atlantic Canada: implications for the vegetation of tropical lowlands during glacial phases

Abstract: New research suggests that Pennsylvanian Coal Forests were commonly replaced by conifer-dominated vegetation during seasonally dry glacial phases. Here we describe palynological assemblages from stacked sequences of the Middle Pennsylvanian (late Moscovian) Sydney Mines Formation of Nova Scotia, Canada, which lends some support to this hypothesis. One critical sample from a widespread redbed succession below the Harbour Coal is dominated by conifer pollen (55%), together with abundant representatives of cordaitaleans, other coniferopsids, and rare pteridosperms, ferns and lepidodendrids. It differs markedly from 13 other samples obtained from coals, their roof shale–limestone and associated channel bodies, which are dominated by lepidodendrids, marattialean tree-ferns, cordaitaleans and/or calamiteans. The latter beds represent coastal wetlands, and are attributed to late transgressive and highstand systems tracts, whereas the conifer-bearing sample represents a dryland alluvial plain and may be attributed to lowstand or earliest transgressive systems tracts. Three additional samples from grey shale below a sequence boundary (late highstand) and between a redbed succession and major coal seam (early to mid-transgressive deposits) contain transitional palynofloras with a high proportion of herbaceous gleicheniaceous and sphenopteroid ferns, herbaceous lycopsids, and sphenophylls interspersed with cordaitaleans and/or lepidodendrids. The dominance of conifer pollen within the dryland components of well-defined sequences, which have been linked to relative sea-level change promoted by Gondwanan glaciation, supports the view that Pennsylvanian tropical biomes responded to the beat of glacial–interglacial cycles.

COMPOSITIONAL CHANGES IN A MID-STEPHANIAN (KASIMOVIAN) FLORA IN RELATION TO ALLUVIAL PLAIN DEPOSITS DERIVED FROM WESTWARD-RECEDING MOUNTAINS AND BORDERED BY THE PALEOTETHYS: LA MAGDALENA COALFIELD, NORTHWESTERN SPAIN

Upper Barruelian, “Saberian,” and Stephanian B (Kasimovian–lower Gzhelian) strata in northwestern Spain represent a strongly subsiding alluvial plain connected to the Paleotethys and adjacent to a mountainous hinterland. The rocks have been deformed into steeply dipping, often isoclinal synclines delimited by foreland-directed thrust faults; a steep basin margin with paleovalleys occurs on the hinterland side. One of these tectonic outliers is the La Magdalena Coalfield, of “Saberian” age, where the quantification of a substantial floral record (140 taxa) from 85 localities in 1200 m of strata allows us to observe changes in floral composition through time matched with broad changes in sedimentary facies corresponding to increased remoteness from a receding basin margin. Within the context of a humid environment, a predominantly fluvial facies changed upward and in time into more generalized semi-lacustrine and peat-forming facies. Although pteridosperms and marattialean tree ferns (pecopterids) are dominant throughout, a proportional increase in tree ferns is observed for the higher part of the succession where calamitaceans become less common and lycopsids more noticeable. These floral changes reflect wetter sedimentary conditions, conducive to the production of coals (high ash) of limited lateral extent.

Landscape gradients and patchiness in riparian vegetation on a Middle Pennsylvanian braided-river plain prone to flood disturbance (Nýřany Member, Central and Western Bohemian Basin, Czech Republic)

We reconstruct the spatial heterogeneity and community ecology of riparian vegetation preserved in fluvial deposits of the upper Asturian to middle(?) Cantabrian (upper Moscovian) Nýřany Member, Central and Western Bohemian Basin, Czech Republic. Poorly fossiliferous channel sandstone and conglomerate dominate at the four localities studied, but fine-grained intercalations, representing abandoned channels, floodplains, and shallow lakes, yielded rich megafloral and palynological assemblages. Sedimentological evidence indicates that high-energy flow characterized a braided-river plain prone to avulsion and flooding. Taphonomic observations and multivariate analysis of 41 quadrats containing mostly (par)autochthonous megafloral assemblages reveal that riparian vegetation comprised a collage of monospecific to low-diversity communities, with patchiness prevalent at local and regional scales. The vertical arrangement of megafloral assemblages provides evidence for ecological succession at some localities, with pioneering sphenopsid-dominated seres being replaced by marattialean tree ferns and then by medullosalean pteridosperms as ponded waters shallowed and exposure increased. At other localities, the composition and structure of megafloral assemblages remains unchanged through thin stratigraphic intervals, indicating short-term persistence and resilience of communities. Non-metric multi-dimensional scaling exposes habitat partitioning between different plant groups, which were organized along ecological gradients controlled by the drainage and stability of substrates. Better-drained and stable channel margins supported long-lived site-occupiers, such as cordaitaleans and monospecific stands of medullosalean pteridosperms. Application of the Patch Dynamics Concept, which predicts patterns of community recovery after disturbance, indicates that these species assemblages were ‘dominance-controlled’ (i.e., contained one or more K-selected species that were competitively superior to all others). Pioneering vegetation comprising fast-growing, opportunistic taxa, particularly ferns and sphenopsids, was most common on wetter, shifting substrates of frequently flooded abandoned channels, low-lying floodplains, and lake margins. In these ‘founder-controlled’ communities, several r-selected species had similar competitive abilities. Ferns, sphenopsids, and various lycopsids dominated swamps, marshes, and ephemeral mires on distal floodplains. The heterogeneous distribution of riparian plants is consistent with that of modern, disturbance-dominated fluvial environments, although Pennsylvanian species richness was much lower. A review of floristic patterns in latest Middle Pennsylvanian vegetation of Euramerica confirms that arborescent ferns proliferated across clastic wetlands during the late Asturian, although medullosalean pteridosperms remained the most important component of most communities. The Nýřany Member seems to be an exception, as pteridosperm relative abundance may have declined dramatically at a level coincident with the fern radiation.

A Middle Pennsylvanian (Bolsovian) peat-forming forest preserved in situ in volcanic ash of the Whetstone Horizon in the Radnice Basin, Czech Republic

The precursory mire of the Middle Pennsylvanian (Bolsovian) Lower Radnice Coal was buried in situ by volcanic ash, preserving the taxonomic composition, spatial distribution, vertical stratification, and synecology of this peat-forming ecosystem in extraordinary detail. Plant fossil remains represent the pre-eruption vegetation of the swamp, which resulted from accumulation of peat in a high-ash, planar (rheotrophic) mire situated in a narrow palaeovalley containing an active fluvial system. A tuff bed (the Bělka) at the base of the volcaniclastic Whetstone Horizon was exposed in two contiguous excavations over an area of 50 m 2 in the Radnice Basin of western Bohemia, Czech Republic. Twenty-seven morphotaxa were identified, representing 20 whole-plant species with a wide variety of growth forms. The canopy of the peat-forming community was dominated by Cordaites borassifolius trees together with the arborescent lycopsid “ Lepidodendron” (= Paralycopodites), whereas Lepidophloios cf. acerosus was subdominant. Evidence suggests that the laterally extensive “crowns” of these arborescent lycopsids would have overlapped during the final phase of their life cycles, but differences in the height of tree species resulted in a complex and vertically variable canopy interrupted by randomly distributed gaps. The understorey was dominated by medullosan pteridosperms and marattialean tree ferns, whereas zygopterid ferns and sphenophylls comprised the bulk of the ground cover. In comparison with the canopy, understorey and ground cover species were less abundant and patchier in distribution, with almost complete absence beneath the deep shade of C. borassifolius trees. Lianas that entwined arborescent trees were an important component of the peat-forming forest. Three lyginopterid pteridosperm species along with a sphenophyll had a lianescent habit based on their close association with upright or prone lycopsid trunks and “canopy” branches. Species richness in the swamp superficially appears low. However, considering the small area of excavation, along with the higher diversity known from the same tuff bed in the adjacent, former opencast Ovčín Mine, it appears that species richness in the forest was comparable to some of the less diverse Westphalian peat-forming swamps in the U.S.A. The Lower Radnice mire vegetation was compositionally homogeneous, but had a heterogeneous distribution with patchiness occurring at a very fine scale. The preserved plant assemblage most resembles mires dominated by medullosan pteridosperms and Paralycopodites described from upper Westphalian coal balls in the U.S.A., which were characterised by high diversity in all storeys and involved plants centred in high-ash peat-forming swamps.

Plant taphonomy and palaeoecology of Stephanian limnic wetlands in the eastern Pyrenees (Catalonia, Spain)

Late Pennsylvanian (Stephanian C) limnic wetlands from the Surroca-Ogassa coalfield, (eastern Pyrenees, Catalonia, Spain) are characterised for the first time based on combined sedimentological, taphonomic, and palaeoecological analysis. Peat mires occurred in floodplain settings, and they were probably formed by monospecific stands of Sigillaria. These mires were swept away by pyroclastic flows, which produced the accumulation and orientation of sigillarian logs on the top of the volcanoclastic deposits. Floodplains were generally devoid of vegetation, with the exception of small sphenopsid stands. Calamites also grew within active fluvial channels. They were accompanied by marattialean tree ferns in low-regime fluvial channels. Medullosan pteridosperms bearing Alethopteris foliage and Pachytesta seeds were extremely abundant in particular horizons and grew probably in floodplain margins covering ancient peat mires. Parautochthonous cordaitalean remains were abundant in distal alluvial deposits.

Aromatized arborane/fernane hydrocarbons as biomarkers for cordaites

Previous palaeobotanical and palynological studies on coals from Euramerican Pennsylvanian ( identical with Late Carboniferous) coal basins indicate a major change in coal-swamp floras, especially at the Westphalian-Stephanian ( approximately Kasimovian-Gzhelian, according to Geological Time Scale 2004) boundary. A flora dominated by arborescent lycophytes was replaced by a vegetation dominated by marattialean tree ferns in various Euramerican coal basins. Earlier combined palynological and organic geochemical studies on Westphalian/Stephanian coals and shales from the Saar-Nahe Basin (Germany) revealed that the distribution of aromatized arborane/fernane hydrocarbons in solvent extracts reflects the increasing importance of seed plants, especially cordaites (extinct group of gymnosperms), conifers and pteridosperms. However, the biological source of the precursor molecules could not be specified. To clarify if the arborane/fernane derivatives MATH, MAPH, DAPH 1, and DAPH 2 in Westphalian/Stephanian coals can be assigned to one of the three potential source plant groups, we analyzed coals, sediments and fossil plant remains from different Euramerican locations with respect to their biomarker composition and stable carbon isotopic composition. Thereby, stable carbon isotopic ratios showed only insignificant variations between Westphalian and Stephanian samples and proved to be an unsuitable tool to describe floral changes during the Westphalian/Stephanian of the Saar-Nahe Basin. In contrast, we were able to show for the first time that MATH, MAPH, DAPH 1 and DAPH 2 are prominent constituents only in extracts of cordaitean macrofossils and can therefore be regarded as biomarkers for this group of gymnosperms.

The ecology of Paleozoic ferns

Ferns or fern-like plants have been important elements of terrestrial vegetation since the Late Devonian. Rhacophyton, a fern-like plant of the Late Devonian, appears to have been a colonizer of wet substrates, often forming large, nearly monotypic stands in peat-accumulating swamps. The earliest true ferns have been found in environments with high levels of disturbance, often fire, which suggest opportunistic, colonizing life histories, consistent with small, scrambling body plans. During the Early Carboniferous all major body plans and life histories of ferns appear, including scrambling ground cover, tree habit, and lianas. These ecological roles are distributed across several major lineages, including the Zygopteridales, Filicales, and Marattiales, plus some fern-like groups of uncertain affinity, and disappear and reappear independently within these groups. Until the Stephanian, the later part of the Late Carboniferous, ferns largely were confined to secondary ecological roles: colonists, understory vegetation, small vines. Beginning in the latter part of the Westphalian and expanding dramatically in the Stephanian, marattialean tree ferns became the dominant trees of tropical lowland, wetland forests. This dominance continued locally into the Permian in wetter parts of the landscape. The Paleozoic ferns suffered major extinctions at several times, beginning in the Late Carboniferous. By the Permian, new lineages were appearing, some of which would persist into and become dominant vegetational components during the Mesozoic. Among these lineages virtually all of the life histories and body plans that characterized Paleozoic ferns would reappear independently, plus some new kinds of organization and ecology, emphasizing the great evolutionary flexibility and responsiveness of fern-like construction and reproductive biology.

Chemotaxonomy for naturally macerated tree-fern cuticles (Medullosales and Marattiales), Carboniferous Sydney and Mabou Sub-Basins, Nova Scotia, Canada

Naturally macerated cuticles (NMC) and one synangium, representing medullosalean and marattialean tree-fern species, from two Carboniferous coalfields in Nova Scotia, Canada, are investigated. The samples were analyzed by infrared spectroscopy (FTIR), and by pyrolysis-gas chromatograph/mass spectrometry (py-Gc/Ms) techniques in search for chemical signatures that would help in developing a chemotaxonomic classification of Carboniferous fern species, assuming genetically dependent make-up of cuticles. FTIR-derived CH 2/CH 3 ratios, in conjunction with contributions from carboxyl groups, demonstrated a better potential for discriminating between medullosalean genera and species than molecular signatures obtained by py-Gc/Ms. However, the latter provided better data for differentiating medullosalean from marattialean tree ferns as a group. Changes in the chemical make-up of naturally macerated cuticles due to sample preparation are discussed.